The proposed work is a continuation of our approach combining behavioral, biochemical and morphologic analysis to chronic effects of methamphetamine. A significant and long lasting depletion of dopamine has been demonstrated in the caudate nucleus of rhesus monkeys treated with methamphetamine. Proposed work will attempt to define the mechanism, permanence and significance of this depletion. Work to demonstrate a morphologic correlate of this finding will continue. Light and electron microscopic evaluation will be utilized. Muscle injury and associated biochemical changes were observed earlier and these will be studied in more detail to describe their pathogenesis and evaluate their severity. Behavioral work will concentrate on evaluation of treated animals' ability to perform finely controlled muscle movements. The morphologic observations of muscle injury suggest that there will be a deficit in performance.